1. Field of the Invention
The present invention relater to a push-switch for a vehicle used for activating or de-activating stop-lamps of a brake pedal operation shaft of an automobile, and a method for manufacturing the same.
2. Description of the Related Art
Hitherto, main controls when a brake pedal of an automobile is operated include activation of stop-lamps for noticing that the brake pedal has been depressed, and cancellation of an automatic drive function for automatically running the automobile at a constant speed. These controls are effected by different switches, or one switch having plural functions.
A conventional push-switch is explained by referring to FIG. 8 to FIG. 11. That is, FIGS. 8-11 depict prior art.
FIG. 8 is a sectional view of a conventional push-switch, and FIG. 9 is its exploded perspective view. A nearly tubular case 1 made of an insulating resin is open at its top, and has an inner bottom. On the inner bottom, a pair of fixed contacts 2 made of a conductive metal plate projecting upwardly along the left inner wall, and a pair of fixed contacts 3 made of a conductive metal plate similarly projecting upwardly and bent in an L-shape at their upper ends, are fixed and planted by fusing or crimping. The contacts 2 have terminals 2B, and the contacts 3 have terminals 3B.
By a contact pressure spring 5, in a slightly depressed coil form disposed between the lower central side of a movable contact 4 made of a conductive metal plate, and the inner bottom of the case 1, both ends of the movable contact 4 elastically abut against the bent lower sides of the fixed contacts 3. That is, the pair of fixed contacts 3 are electrically connected through the movable contact 4 via contact portions 3A and 4A.
An operation shaft 6 is accommodated in the case 1 and is movable vertically. A fixing part 7A at one end of a contact piece 7 made of a thin elastic metal plate is held and fixed at the side of the operation shaft 6 by means of a rivet 8, an intermediate arm 7C is slightly deflected, and a contact part 7B at another end elastically abuts the left inner wall of the case 1.
An operation spring 9 in a slightly depressed coil form disposed between the lower sidle of the operation shaft 6 and the inner bottom of the case 1 thrusts the operation shaft 6 upwardly. The opening 1A of the case 1 is closed with a cover 10. The cover 10 has a threaded bearing 10A. The operation shaft 6 is inserted into a central penetration hole 10B of the bearing 10A, and a push-switch 11 is composed.
In the push-switch having such structure, first, the pair of fixed contacts 2 and fixed contacts 3 are fixed on the inner bottom of the case 1 by fusing or crimping. Then, the movable contact 4 and slightly depressed contact pressure spring 5 are inserted between the inner bottom of the case 1 and the fixed contacts 3, and both ends of the movable contact 4 elastically abut the bent lower sides of the pair of fixed contacts 3 via contact portions 3A and 4A.
By the rivet 8, the operation shaft 6 holding and fixing the contact piece 7 at its side is put into the case 1, while depressing the operation spring 9 placed against the inner bottom of the case 1. By the cover 10 having the operation shaft 6 inserted in the penetration hole 10B, the opening of the case 1 is closed, and the push-switch 11 is completed.
In this structure, by pushing the upper side of the operation shaft 6 projecting from the penetration hole 10B, as shown in a sectional view in FIG. 10, the operation shaft 6 moves downwardly while depressing the operation spring 9. As a result, the contact part 7B of the contact piece 7 held at the side of the operation shaft 6 elastically slides on the left inner wall of the case 1, and comes into contact with the fixed contacts 2. That is, the pair of fixed contacts 2 are electrically connected by way of the contact piece 7.
At the same time, the lower side of the operation shaft 6 pushes the upper central side of the movable contact 4, and the contact pressure spring 5 is depressed, and both ends or contact portions 4A of the movable contact 4 depart from the bent lower sides or contact portions 3A of the pair of fixed contacts 3, and the pair of fixed contacts 3 are electrically isolated.
As shown in a side view in FIG. 11, in the state that the operation shaft 6 is depressed by angle member 12B formed integrally with brake pedal 12, the outer circumference of the bearing 10A of push-switch 11 is mounted on a car body by a stopper 13. The angle member 12B is held on the car body rotatably by means of an upper end support 12A.
Further, as shown in FIG. 11, a connector 14 is fitted to the push-switch 11. The fixed contacts 2 are connected to an electronic circuit 16 for controlling the automatic drive function for keeping the running speed constant, through a power supply unit 15. The fixed contacts 3 are further connected to stop-lamp 17 through the power supply unit 15.
Thus, in the depressed state of the operation shaft 6 of the push-switch 11; that is, in the running state of an automobile, as shown in FIG. 10, since the fixed contacts 2 are electrically connected through the contact piece 7, the automatic drive function of the electronic circuit 16 is in an active state. At this time, the stop-lamp connected to the fixed contacts 3 is in a de-activated state.
When stepping on the brake pedal 12 as shown in FIG. 11, the angle member 12B rotates about the support 12A, and departs from the operation shaft 6 of the push switch 11. As a result, the operation shaft 6 returns to the state shown in FIG. 8 by the thrusting force of the contact pressure spring 5 and operation spring 9, and the contact piece 7 departs from the fixed contacts 2, and the automatic drive function of the electronic circuit 16 is canceled.
At the same time, by the thrusting force of the contact pressure spring 5, both ends of the movable contact 4 come into contact with the bent lower sides of the pair of fixed contacts 3 via contact portions 3A and 4A, and hence the stop-lamps 17 are activated. As a result, stepping on the brake pedal 12 is noticed.
In the conventional push-switch; however, the contact piece 7 of a thin elastic metal plate is likely to be deformed when holding and fixing the contact piece 7 to the side of the operation shaft 6 by the rivet 8, or when assembling the operation shaft 6, holding this contact piece 7, into the case 1. It also takes much time to assemble the switch.
The invention is devised in light of the conventional problems, and it is hence an object thereof to present an easy-to-assemble and inexpensive push-switch capable of obtaining a stable contact of contacts, and a method for manufacturing the same.
The push-switch of the invention comprises:
a tubular case made of an insulating resin with an open top and having an inner bottom;
a pair of fixed contacts planted on the inner bottom of the case and projecting upwardly;
an operation shaft vertically movable and accommodated in the case;
a contact piece of a thin elastic metal plate, with a fixing part at one end held at the side of the operation shaft, with an intermediate arm slightly deflected, and with a contact part at another end elastically sliding on fixed contacts by vertical movement of the operation shaft;
an operation spring in a coil form installed in the case in a slightly depressed state and thrusting the operation shaft upwardly; and
a cover having a penetration hole in the center thereof for inserting the operation shaft for closing the opening of the case.
The operation shaft has a holding part at its side, and the holding part has a nearly U-shaped groove at both its ends, and a recess with an open upper end formed in its center. The fixing part of the contact piece is inserted into the groove of the holding part from beneath, and a tongue at an upper side and projecting from both ends of the fixing part of the contact piece abuts the lower side of the groove, while a protrusion projecting in the direction of the operation shaft from the center of the fixing part of the contact piece is engaged with the lower end of the recess of the holding part.
The push-switch of the invention further includes, at the lower side of the cover, a pair of ribs projecting downwardly with their inner sides flush with the contact surface of the fixed contact, and the contact part of the contact piece elastically abuts against the inner side of each rib.
The manufacturing method of the push-switch of the invention comprises, in the push-switch having the above structure, the steps of: (a) holding the fixing part of the contact piece in the holding part at the side of the operation shaft; (b) inserting the operation shaft into a penetration hole in the center of the cover; (c) temporarily holding the operation shaft on the cover, with the contact part of the contact piece elastically abutting the inner side of the ribs; and (d) combining the cover, temporarily holding the operation shaft, and the case.